KARYOKINESIS AND ITS RELATION TO FERTILIZATION. 225 
fied that Flemming (‘ Arch. f. mikr. Anat.” Bd. xviii, p. 233, 
et seq.) has recognised in the salamander that only the chro- 
matin forms the head of the spermatozoon. However, the 
matter requires further research. 
Before I proceed further as to what we know of the act of 
fusion, it is now necessary to mention another matter which 
seems to stand in close relation to the process of fertilization, 
namely, the formation of the so-called “ directive corpuscles” 
(Richtungskorperchen). 
By “directive corpuscles” (or “ globes polaires ” of Robin) 
is meant the small, roundish bodies which are extruded 
from the fully formed egg, usually before impregnation, and 
(in many cases) independently of the entrance of the sperma- 
tozoon into the egg. The directive corpuscles are of consider- 
ably smaller dimensions than the egg itself (see Pl. XIV, 
fig. 14). 
It has required a long list of workers,—I mention especially 
F. Miller (141), Robin (173), Butschli (40—43), Lovén (128), 
Flemming (63 a), Bellonci (16 a, 16 0), Fol (66, 67), O. Hertwig 
(93), Hensen (88—90), Oellacher (150), Calberla (45), Kupffer 
(117—120), Oskar Schultze (182), and E. van Beneden (23),— 
before we have been able to form some idea as to the process of 
the formation of directive corpuscles; and even yet all the points 
are not cleared up. As to their physiological significance very 
important differences of opinion still exist, and as to these I will 
enter into greater detail later on. The name “ Richtungskor- 
perchen ” (properly “ Richtungsblasen ”) was given to them by 
Fr. Miller, because their point of origin stands in relation to 
the place where the first division of the egg will later on make 
its appearance. We now know that these bodies are destined 
to be lost, and that their extrusion is not caused by the act of 
fertilization, since, as A. Hensen has shown in the case of the 
mammalian egg, they are already present before the entrance 
of the spermatozoon into the egg, even whilst the egg is still in 
the Graafian follicle. The extrusion of the directive corpuscles is 
therefore an act connected with the maturation of the egg-cell, 
whether this will be fertilized later on or not. But it is still 
